For -4+3,
1. start with zero
2. move to left (-x axis) for 4 units (-4)
3. then move to right (+x axis) for 3 units (+3)
For 3+(-4)
1. Start with zero
2. Move the point to right side by 3 units (+3)
3. then move the point to the left by 4 units (-4)
For both you'll stop at -1.